[_Mazza_]

Most people shop on multiple websites, most people don't carry around two phones.

[shawnz]

Most people also don't pay for a subscription service that gives you cheaper prices. If you look specifically at Prime subscribers, I bet you'd find that they make efforts to do all their shopping through Amazon where possible.

[zimbatm]

In this context, the Phone is supposed to be on the same network for latency reasons. Having multiple phones at home is not a big issue.